Wireless communication method using TXOP and wireless communication terminal using same

ABSTRACT

Provided is a wireless communication terminal that wirelessly communicates. The wireless communication terminal includes: a transceiver for transmitting and receiving a wireless signal; and a processor for processing the wireless signal. The processor is configured to perform a transmission based on a transmission opportunity (TXOP) limit which is a maximum value of a TXOP, which is a time interval in which a wireless communication terminal has a right to initiate a frame exchange sequence in a wireless medium.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/503,486 filed on Jul. 4, 2019, which is a continuation ofInternational Patent Application No. PCT/KR2018/000447 filed on Jan. 9,2018, which claims the priority to Korean Patent Application No.10-2017-0003137 filed in the Korean Intellectual Property Office on Jan.9, 2017, Korean Patent Application No. 10-2017-0008306 filed in theKorean Intellectual Property Office on Jan. 17, 2017, Korean PatentApplication No. 10-2017-0024265 filed in the Korean IntellectualProperty Office on Feb. 23, 2017, and Korean Patent Application No.10-2017-0057098 filed in the Korean Intellectual Property Office on May5, 2017, the entire contents of which are incorporated herein byreference.

TECHNICAL FIELD

The present invention relates to a wireless communication method and awireless communication terminal using TXOP.

BACKGROUND ART

In recent years, with supply expansion of mobile apparatuses, a wirelesscommunication technology that can provide a rapid wireless Internetservice to the mobile apparatuses has been significantly spotlighted.The wireless communication technology allows mobile apparatusesincluding a smart phone, a smart pad, a laptop computer, a portablemultimedia player, an embedded apparatus, and the like to wirelesslyaccess the Internet in home or a company or a specific service providingarea.

One of most famous wireless communication technology is wireless LANtechnology. Institute of Electrical and Electronics Engineers (IEEE)802.11 has commercialized or developed various technological standardssince an initial wireless LAN technology is supported using frequenciesof 2.4 GHz. First, the IEEE 802.11b supports a communication speed of amaximum of 11 Mbps while using frequencies of a 2.4 GHz band. IEEE802.11a which is commercialized after the IEEE 802.11b uses frequenciesof not the 2.4 GHz band but a 5 GHz band to reduce an influence byinterference as compared with the frequencies of the 2.4 GHz band whichare significantly congested and improves the communication speed up to amaximum of 54 Mbps by using an Orthogonal Frequency DivisionMultiplexing (OFDM) technology. However, the IEEE 802.11a has adisadvantage in that a communication distance is shorter than the IEEE802.11b. In addition, IEEE 802.11g uses the frequencies of the 2.4 GHzband similarly to the IEEE 802.11b to implement the communication speedof a maximum of 54 Mbps and satisfies backward compatibility tosignificantly come into the spotlight and further, is superior to theIEEE 802.11a in terms of the communication distance.

Moreover, as a technology standard established to overcome a limitationof the communication speed which is pointed out as a weak point in awireless LAN, IEEE 802.11n has been provided. The IEEE 802.11n aims atincreasing the speed and reliability of a network and extending anoperating distance of a wireless network. In more detail, the IEEE802.11n supports a high throughput (HT) in which a data processing speedis a maximum of 540 Mbps or more and further, is based on a multipleinputs and multiple outputs (MIMO) technology in which multiple antennasare used at both sides of a transmitting unit and a receiving unit inorder to minimize a transmission error and optimize a data speed.Further, the standard can use a coding scheme that transmits multiplecopies which overlap with each other in order to increase datareliability.

As the supply of the wireless LAN is activated and further, applicationsusing the wireless LAN are diversified, the need for new wireless LANsystems for supporting a higher throughput (very high throughput (VHT))than the data processing speed supported by the IEEE 802.11n has comeinto the spotlight. Among them, IEEE 802.11ac supports a wide bandwidth(80 to 160 MHz) in the 5 GHz frequencies. The IEEE 802.11ac standard isdefined only in the 5 GHz band, but initial 11ac chipsets will supporteven operations in the 2.4 GHz band for the backward compatibility withthe existing 2.4 GHz band products. Theoretically, according to thestandard, wireless LAN speeds of multiple stations are enabled up to aminimum of 1 Gbps and a maximum single link speed is enabled up to aminimum of 500 Mbps. This is achieved by extending concepts of awireless interface accepted by 802.11n, such as a wider wirelessfrequency bandwidth (a maximum of 160 MHz), more MIMO spatial streams (amaximum of 8), multi-user MIMO, and high-density modulation (a maximumof 256 QAM). Further, as a scheme that transmits data by using a 60 GHzband instead of the existing 2.4 GHz/5 GHz, IEEE 802.11ad has beenprovided. The IEEE 802.11ad is a transmission standard that provides aspeed of a maximum of 7 Gbps by using a beamforming technology and issuitable for high bit rate moving picture streaming such as massive dataor non-compression HD video. However, since it is difficult for the 60GHz frequency band to pass through an obstacle, it is disadvantageous inthat the 60 GHz frequency band can be used only among devices in ashort-distance space.

Meanwhile, in recent years, as next-generation wireless communicationtechnology standards after the 802.11ac and 802.11ad, discussion forproviding a high-efficiency and high-performance wireless communicationtechnology in a high-density environment is continuously performed. Thatis, in a next-generation wireless communication technology environment,communication having high frequency efficiency needs to be providedindoors/outdoors under the presence of high-density terminals and baseterminals and various technologies for implementing the communicationare required.

Especially, as the number of devices using a wireless communicationtechnology increases, it is necessary to efficiently use a predeterminedchannel Therefore, required is a technology capable of efficiently usingbandwidths by simultaneously transmitting data between a plurality ofterminals and base terminals.

DISCLOSURE Technical Problem

An object of an embodiment of the present invention is to provide awireless communication terminal using TXOP.

Technical Solution

According to an embodiment of the present invention, a wirelesscommunication terminal that wirelessly communicates includes: atransceiver for transmitting and receiving a wireless signal; and aprocessor for processing the wireless signal. The processor isconfigured to perform a transmission based on a transmission opportunity(TXOP) limit which is a maximum value of a TXOP, which is a timeinterval in which a wireless communication terminal has a right toinitiate a frame exchange sequence in a wireless medium.

The processor may be configured to transmit a Beamforming Report Poll(BRP) trigger frame to another wireless communication terminal using aTXOP exceeding a TXOP limit, and receive a feedback frame in response tothe BRP trigger frame from the another wireless communication terminalwithin the TXOP exceeding the TXOP limit. In this case, the BRP triggerframe may trigger simultaneous transmission of feedback frames of one ormore wireless communication terminals. In addition, the feedback framemay indicate a state of a channel measured by the another wirelesscommunication terminal, which is to be used for a Multi Input MultiOutput (MIMO) transmission to the another wireless communicationterminal of the wireless communication terminal or is to be used for abeamforming transmission to the another wireless communication terminalof the wireless communication terminal.

After a predetermined time from when the wireless communication terminaltransmits a Null Data Packet Announcement (NDPA) frame informing theanother wireless communication terminal that a sounding protocolsequence is initiated, the processor may be configured to transmit aNull Data Packet (NDP) frame to be used for a state measurement of thechannel to the another wireless communication terminal. In this case,when the wireless communication terminal transmits the NDPA frame, theNDP frame, and the BRP trigger frame within the TXOP limit, theprocessor may be configured to transmit the BRP trigger frame to theanother wireless communication terminal using the TXOP exceeding theTXOP limit after a predetermined time from when the wirelesscommunication terminal transmits the NDP frame to the another wirelesscommunication terminal.

When the wireless communication terminal transmits the BRP trigger framewithin the TXOP limit, the processor may be configured to transmit theBRP trigger frame using the TXOP exceeding the TXOP limit.

The feedback frame may be transmitted from the another wirelesscommunication terminal after a predetermined time from when the anotherwireless communication terminal receives the BRP trigger frame.

The processor may be configured to use dynamic fragmentation to generateat least one fragment, and transmit the at least one fragment to anotherwireless communication terminal. In this case, the dynamic fragmentationrepresents a fragment that is not a static fragmentation that isrequired to equally fragment the size of all fragments except the lastfragment.

The processor may be configured to foremost generate a first fragment ofthe at least one fragment based on a value that the another wirelesscommunication terminal designates as a minimum size of a fragment, andtransmit the first fragment to the another wireless communicationterminal using the TXOP exceeding the TXOP limit.

When the wireless communication terminal transmits the at least onefragment to the another wireless communication terminal without using anAggregate (A)-MPDU including a plurality of MAC Protocol Data Units(MPDUs), the processor may be configured to transmit the first fragmentto the another wireless communication terminal using the TXOP exceedingthe TXOP limit.

The processor may be configured to generate the first fragment with asize equal to a value that the another wireless communication terminaldesignates as a minimum size of a fragment.

The processor may be configured to generate the at least one fragment bythe maximum number of fragments that the wireless communication terminalis capable of generating, and transmit a first fragment generated lastamong the at least one fragment to the another wireless communicationterminal using the TXOP exceeding the TXOP limit.

The maximum number of fragments that the wireless communication terminalis capable of generating may be 16.

When the another wireless communication terminal explicitly fails toreceive a first fragment, which is one of the at least one fragment,based on at least one of whether the wireless communication terminaldoes not transmit a fragment following the first fragment and whetherthe another wireless communication terminal explicitly fails to receivea fragment following the first fragment, the processor may be configuredto generate a fourth fragment having a size different from the thirdfragment and having a sequence number and a fragment number that are thesame as a sequence number and a fragment number of the third fragment.In this case, the processor may be configured to transmit the fourthfragment to the another wireless communication terminal instead ofretransmitting the third fragment to the another wireless communicationterminal.

When there is no BlockACK agreement between the wireless communicationterminal and the another wireless communication terminal, the processormay be configured to perform dynamic fragmentation according to afragmentation level determined according to the capability of theanother wireless communication terminal. In this case, the fragmentationlevel may indicate a transmission method of a fragment.

The wireless communication terminal may be a TXOP holder.

According to an embodiment of the present invention, an operation methodof a wireless communication terminal that wirelessly communicatesincludes: performing a transmission based on a transmission opportunity(TXOP) limit which is a maximum value of a TXOP, which is a timeinterval in which a wireless communication terminal has a right toinitiate a frame exchange sequence in a wireless medium.

The performing the transmission based on the TXOP limit may include:transmitting a Beamforming Report Poll (BRP) trigger frame to anotherwireless communication terminal using a TXOP exceeding a TXOP limit, andreceiving a feedback frame in response to the BRP trigger frame from theanother wireless communication terminal within the TXOP exceeding theTXOP limit. In this case, the BRP trigger frame may trigger simultaneoustransmission of feedback frames of one or more wireless communicationterminals. In this case, the feedback frame may indicate a state of achannel measured by the another wireless communication terminal, whichis to be used for a Multi Input Multi Output (MIMO) transmission to theanother wireless communication terminal of the wireless communicationterminal or is to be used for a beamforming transmission to the anotherwireless communication terminal of the wireless communication terminal.

The transmitting the BRP trigger frame may include: after apredetermined time from when the wireless communication terminaltransmits a Null Data Packet Announcement (NDPA) frame informing theanother wireless communication terminal that a sounding protocolsequence is initiated, receiving, by the another wireless communication,a Null Data Packet (NDP) frame to be used for the channel statemeasurement, and when the wireless communication terminal transmits theNDPA frame, the NDP frame, and the BRP trigger frame within the TXOPlimit, transmitting the BRP trigger frame using the TXOP exceeding theTXOP limit after a predetermined time from when the wirelesscommunication terminal transmits the NDP frame to the another wirelesscommunication terminal.

The transmitting the BRP trigger frame using the TXOP exceeding the TXOPlimit may include when transmitting the BRP trigger frame within theTXOP limit, transmitting the BRP trigger frame using the TXOP exceedingthe TXOP limit.

The method may further include using dynamic fragmentation to generateat least one fragment, wherein the performing of the transmission basedon the TXOP limit may include transmitting the at least one fragment toanother wireless communication terminal. In this case, the dynamicfragmentation may represent a fragment that is not a staticfragmentation that is required to equally fragment the size of allfragments except the last fragment.

The generating the at least one fragment may include foremost generatinga first fragment of the at least one fragment based on a value that theanother wireless communication terminal designates as a minimum size ofa fragment, the transmitting the at least one fragment to the anotherwireless communication terminal may include transmitting the firstfragment to the another wireless communication terminal using the TXOPexceeding the TXOP limit.

The foremost generating of the first fragment among the at least onefragment may include generating the first fragment with a size equal toa value that the another wireless communication terminal designates as aminimum size of a fragment.

The generating the at least one fragment includes generating the atleast one fragment by a maximum number of fragments that the wirelesscommunication terminal is capable of generating, and the transmitting ofthe at least one fragment to another wireless communication terminalincludes transmitting a second fragment, which is last generated amongthe at least one fragment, to the another wireless communicationterminal using the TXOP exceeding the TXOP limit.

The operating method may include, when the another wirelesscommunication terminal explicitly fails to receive a third fragment,which is one of the at least one fragment, generating a fourth fragmenthaving a size different from a size of the third fragment forretransmission, and having a sequence number and fragment number whichare same as a sequence number and fragment number of the third fragmentfor retransmission of the third fragment based on at least one ofwhether the wireless communication terminal transmits a fragmentfollowing the third fragment or whether the another wirelesscommunication terminal explicitly fails to receive a fragment followingthe third fragment; and transmitting the fourth fragment to the anotherwireless communication terminal instead of retransmitting the thirdfragment to the another wireless communication terminal.

Advantageous Effects

An embodiment of the present invention provides a wireless communicationmethod using TXOP and a wireless communication terminal using the same.

DESCRIPTION OF DRAWINGS

FIG. 1 shows a wireless LAN system according to an embodiment of thepresent invention.

FIG. 2 shows a wireless LAN system according to another embodiment ofthe present invention.

FIG. 3 shows a block diagram illustrating a configuration of a stationaccording to an embodiment of the inventive concept.

FIG. 4 shows a block diagram illustrating a configuration of an accesspoint according to an embodiment of the present invention.

FIG. 5 shows a process that a station sets an access point and a linkaccording to an embodiment of the present invention.

FIG. 6 shows an operation in which a wireless communication terminalperforms a frame exchange based on a TXOP limit according to anembodiment of the present invention.

FIG. 7 shows that a wireless communication terminal according to anembodiment of the present invention dynamically performs fragmentation.

FIG. 8 shows an operation of a wireless communication terminal accordingto an embodiment of the present invention to determine a recipientreception failure and a retransmission operation.

FIGS. 9 to 10 illustrate operations in which a wireless communicationterminal according to an embodiment of the present invention performsretransmission within a TXOP limit.

FIG. 11 shows an operation in which a wireless communication terminalaccording to another embodiment of the present invention retransmitsfragments included in the same sequence as a retransmitted fragmentafter retransmission within a TXOP limit.

FIGS. 12 to 13 show a transmission operation exceeding a TXOP limit whena wireless communication terminal according to an embodiment of thepresent invention uses dynamic fragmentation.

FIG. 14 shows a retransmitting operation of a wireless communicationterminal, not a TXOP holder, according to an embodiment of the presentinvention.

FIGS. 15 to 16 show a retransmitting operation of a wirelesscommunication terminal, not a TXOP holder, according to anotherembodiment of the present invention.

FIGS. 17 to 18 show that the wireless communication terminal accordingto an embodiment of the present invention performs the sounding protocoloperation in relation to the TXOP limit.

FIG. 19 shows the operation of a wireless communication terminalaccording to an embodiment of the present invention.

MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention will be described belowin more detail with reference to the accompanying drawings. The presentinvention may, however, be embodied in different forms and should not beconstructed as limited to the embodiments set forth herein. Parts notrelating to description are omitted in the drawings in order to clearlydescribe the present invention and like reference numerals refer to likeelements throughout.

Furthermore, when it is described that one comprises (or includes orhas) some elements, it should be understood that it may comprise (orinclude or has) only those elements, or it may comprise (or include orhave) other elements as well as those elements if there is no specificlimitation.

This application claims priority to and the benefit of Korean PatentApplication Nos. 10-2017-0003137 (2017 Jan. 9), Nos. 10-2017-0008306(2017 Jan. 17), Nos. 10-2017-0024265 (2017 Feb. 23), and Nos.10-2017-0057098 (2017 May 5) filed in the Korean Intellectual PropertyOffice and the embodiments and mentioned items described in therespective applications are included in the Detailed Description of thepresent application.

FIG. 1 is a diagram illustrating a wireless communication systemaccording to an embodiment of the present invention. For convenience ofdescription, an embodiment of the present invention is described throughthe wireless LAN system. The wireless LAN system includes one or morebasic service sets (BSS) and the BSS represents a set of apparatuseswhich are successfully synchronized with each other to communicate witheach other. In general, the BSS may be classified into an infrastructureBSS and an independent BSS (IBSS) and FIG. 1 illustrates theinfrastructure BSS between them.

As illustrated in FIG. 1, the infrastructure BSS (BSS1 and BSS2)includes one or more stations STA1, STA2, STA3, STA4, and STA5, accesspoints PCP/AP-1 and PCP/AP-2 which are stations providing a distributionservice, and a distribution system (DS) connecting the multiple accesspoints PCP/AP-1 and PCP/AP-2.

The station (STA) is a predetermined device including medium accesscontrol (MAC) following a regulation of an IEEE 802.11 standard and aphysical layer interface for a wireless medium, and includes both anon-access point (non-AP) station and an access point (AP) in a broadsense. Further, in the present specification, a term ‘terminal’ may beused to refer to a concept including a wireless LAN communication devicesuch as non-AP STA, or an AP, or both terms. A station for wirelesscommunication includes a processor and a transceiver and according tothe embodiment, may further include a user interface unit and a displayunit. The processor may generate a frame to be transmitted through awireless network or process a frame received through the wirelessnetwork and besides, perform various processing for controlling thestation. In addition, the transceiver is functionally connected with theprocessor and transmits and receives frames through the wireless networkfor the station.

The access point (AP) is an entity that provides access to thedistribution system (DS) via wireless medium for the station associatedtherewith. In the infrastructure BSS, communication among non-APstations is, in principle, performed via the AP, but when a direct linkis configured, direct communication is enabled even among the non-APstations. Meanwhile, in the present invention, the AP is used as aconcept including a personal BSS coordination point (PCP) and mayinclude concepts including a centralized controller, a base station(BS), a node-B, a base transceiver system (BTS), and a site controllerin a broad sense.

A plurality of infrastructure BSSs may be connected with each otherthrough the distribution system (DS). In this case, a plurality of BSSsconnected through the distribution system is referred to as an extendedservice set (ESS).

FIG. 2 illustrates an independent BSS which is a wireless communicationsystem according to another embodiment of the present invention. Forconvenience of description, another embodiment of the present inventionis described through the wireless LAN system. In the embodiment of FIG.2, duplicative description of parts, which are the same as or correspondto the embodiment of FIG. 1, will be omitted.

Since a BSS3 illustrated in FIG. 2 is the independent BSS and does notinclude the AP, all stations STA6 and STA7 are not connected with theAP. The independent BSS is not permitted to access the distributionsystem and forms a self-contained network. In the independent BSS, therespective stations STA6 and STA7 may be directly connected with eachother.

FIG. 3 is a block diagram illustrating a configuration of a station 100according to an embodiment of the present invention.

As illustrated in FIG. 3, the station 100 according to the embodiment ofthe present invention may include a processor 110, a transceiver 120, auser interface unit 140, a display unit 150, and a memory 160.

First, the transceiver 120 transmits and receives a wireless signal suchas a wireless LAN physical layer frame, or the like and may be embeddedin the station 100 or provided as an exterior. According to theembodiment, the transceiver 120 may include at least one transmit andreceive module using different frequency bands. For example, thetransceiver 120 may include transmit and receive modules havingdifferent frequency bands such as 2.4 GHz, 5 GHz, and 60 GHz. Accordingto an embodiment, the station 100 may include a transmit and receivemodule using a frequency band of 6 GHz or more and a transmit andreceive module using a frequency band of 6 GHz or less. The respectivetransmit and receive modules may perform wireless communication with theAP or an external station according to a wireless LAN standard of afrequency band supported by the corresponding transmit and receivemodule. The transceiver 120 may operate only one transmit and receivemodule at a time or simultaneously operate multiple transmit and receivemodules together according to the performance and requirements of thestation 100. When the station 100 includes a plurality of transmit andreceive modules, each transmit and receive module may be implemented byindependent elements or a plurality of modules may be integrated intoone chip.

Next, the user interface unit 140 includes various types of input/outputmeans provided in the station 100. That is, the user interface unit 140may receive a user input by using various input means and the processor110 may control the station 100 based on the received user input.Further, the user interface unit 140 may perform output based on acommand of the processor 110 by using various output means.

Next, the display unit 150 outputs an image on a display screen. Thedisplay unit 150 may output various display objects such as contentsexecuted by the processor 110 or a user interface based on a controlcommand of the processor 110, and the like. Further, the memory 160stores a control program used in the station 100 and various resultingdata. The control program may include an access program required for thestation 100 to access the AP or the external station.

The processor 110 of the present invention may execute various commandsor programs and process data in the station 100. Further, the processor110 may control the respective units of the station 100 and control datatransmission/reception among the units. According to the embodiment ofthe present invention, the processor 110 may execute the program foraccessing the AP stored in the memory 160 and receive a communicationconfiguration message transmitted by the AP. Further, the processor 110may read information on a priority condition of the station 100 includedin the communication configuration message and request the access to theAP based on the information on the priority condition of the station100. The processor 110 of the present invention may represent a maincontrol unit of the station 100 and according to the embodiment, theprocessor 110 may represent a control unit for individually controllingsome component of the station 100, for example, the transceiver 120, andthe like. The processor 110 may be a modulator and/or demodulator whichmodulates wireless signal transmitted to the transceiver 120 anddemodulates wireless signal received from the transceiver 120. Theprocessor 110 controls various operations of wireless signaltransmission/reception of the station 100 according to the embodiment ofthe present invention. A detailed embodiment thereof will be describedbelow.

The station 100 illustrated in FIG. 3 is a block diagram according to anembodiment of the present invention, where separate blocks areillustrated as logically distinguished elements of the device.Accordingly, the elements of the device may be mounted in a single chipor multiple chips depending on design of the device. For example, theprocessor 110 and the transceiver 120 may be implemented while beingintegrated into a single chip or implemented as a separate chip.Further, in the embodiment of the present invention, some components ofthe station 100, for example, the user interface unit 140 and thedisplay unit 150 may be optionally provided in the station 100.

FIG. 4 is a block diagram illustrating a configuration of an AP 200according to an embodiment of the present invention.

As illustrated in FIG. 4, the AP 200 according to the embodiment of thepresent invention may include a processor 210, a transceiver 220, and amemory 260. In FIG. 4, among the components of the AP 200, duplicativedescription of parts which are the same as or correspond to thecomponents of the station 100 of FIG. 2 will be omitted.

Referring to FIG. 4, the AP 200 according to the present inventionincludes the transceiver 220 for operating the BSS in at least onefrequency band. As described in the embodiment of FIG. 3, thetransceiver 220 of the AP 200 may also include a plurality of transmitand receive modules using different frequency bands. That is, the AP 200according to the embodiment of the present invention may include two ormore transmit and receive modules among different frequency bands, forexample, 2.4 GHz, 5 GHz, and 60 GHz together. Preferably, the AP 200 mayinclude a transmit and receive module using a frequency band of 6 GHz ormore and a transmit and receive module using a frequency band of 6 GHzor less. The respective transmit and receive modules may performwireless communication with the station according to a wireless LANstandard of a frequency band supported by the corresponding transmit andreceive module. The transceiver 220 may operate only one transmit andreceive module at a time or simultaneously operate multiple transmit andreceive modules together according to the performance and requirementsof the AP 200.

Next, the memory 260 stores a control program used in the AP 200 andvarious resulting data. The control program may include an accessprogram for managing the access of the station. Further, the processor210 may control the respective units of the AP 200 and control datatransmission/reception among the units. According to the embodiment ofthe present invention, the processor 210 may execute the program foraccessing the station stored in the memory 260 and transmitcommunication configuration messages for one or more stations. In thiscase, the communication configuration messages may include informationabout access priority conditions of the respective stations. Further,the processor 210 performs an access configuration according to anaccess request of the station. The processor 210 may be a modulatorand/or demodulator which modulates wireless signal transmitted to thetransceiver 220 and demodulates wireless signal received from thetransceiver 220. The processor 210 controls various operations such asradio signal transmission/reception of the AP 200 according to theembodiment of the present invention. A detailed embodiment thereof willbe described below.

FIG. 5 is a diagram schematically illustrating a process in which a STAsets a link with an AP.

Referring to FIG. 5, the link between the STA 100 and the AP 200 is setthrough three steps of scanning, authentication, and association in abroad way. First, the scanning step is a step in which the STA 100obtains access information of BSS operated by the AP 200. A method forperforming the scanning includes a passive scanning method in which theAP 200 obtains information by using a beacon message (S101) which isperiodically transmitted and an active scanning method in which the STA100 transmits a probe request to the AP (S103) and obtains accessinformation by receiving a probe response from the AP (S105).

The STA 100 that successfully receives wireless access information inthe scanning step performs the authentication step by transmitting anauthentication request (S107 a) and receiving an authentication responsefrom the AP 200 (S107 b). After the authentication step is performed,the STA 100 performs the association step by transmitting an associationrequest (S109 a) and receiving an association response from the AP 200(S109 b).

Meanwhile, an 802.1X based authentication step (S111) and an IP addressobtaining step (S113) through DHCP may be additionally performed. InFIG. 5, the authentication server 300 is a server that processes 802.1Xbased authentication with the STA 100 and may be present in physicalassociation with the AP 200 or present as a separate server.

In a specific embodiment, the AP 200 may be a wireless communicationterminal that allocates a communication medium resource and performsscheduling in an independent network, such as an ad-hoc network, whichis not connected to an external distribution service. In addition, theAP 200 may be at least one of a base station, an eNB, and a transmissionpoint TP. The AP 200 may also be referred to as a base wirelesscommunication terminal.

The base wireless communication terminal may be a wireless communicationterminal that allocates and schedules medium resources in communicationwith a plurality of wireless communication terminals. Specifically, thebase wireless communication terminal may serve as a cell coordinator. Ina specific embodiment, the base wireless communication terminal may be awireless communication terminal that allocates and schedulescommunication medium resources in an independent network, such as anad-hoc network, that is not connected to an external distributionservice.

The wireless communication terminal may fragment the traffic to transmitthe traffic. In this case, the traffic may include at least one of a MACservice data unit (MSDU), an aggregate (A)-MSDU, and a managementprotocol data unit (MMPDU). Specifically, the wireless communicationterminal may fragment and transmit at least one of one MSDU, one A-MSDU,and one MMPDU. For convenience of explanation, a portion of an MSDU, aportion of an A-MSDU, or a portion of an MMPDU, which are generatedthrough fragmentation, is referred to as a fragment. In addition, awireless communication terminal that transmits data is referred to as anoriginator, and a wireless communication terminal that receives data isreferred to as a recipient.

Specifically, the wireless communication terminal may generate aplurality of fragments by fragmenting at least one of an MSDU, anA-MSDU, and an MMPDU. In this case, the wireless communication terminalmay transmit the generated plurality of fragments using a plurality ofMPDUs. In addition, the wireless communication terminal receiving aplurality of fragments may defragment a plurality of fragments to obtainat least one of one MSDU, one A-MSDU, and one MMPDU. In this case, theMPDU may be an S-MPDU or an A-MPDU.

The recipient needs sufficient buffer capacity and processing capacityto defragment a plurality of fragments. For this, the originator isrequired to know the fragmentation level that the recipient may support.In this case, the fragmentation level can indicate the transmissionmethod of the fragment. Therefore, the wireless communication terminalmay signal the fragmentation level supported by the wirelesscommunication terminal. The fragmentation level may be divided into fourlevels. Level 0 may indicate that the wireless communication terminal isnot capable of fragmenting for the received MSDU. Also, level 1 mayindicate that the wireless communication terminal is capable ofreceiving an MPDU that includes one fragment. In this case, the MPDU maybe a single MPDU that is not aggregated with another MPDU, or an MPDUthat is not an A-MPDU. Also, level 2 may indicate that the wirelesscommunication terminal is capable of receiving an A-MPDU that includesone fragment per MSDU. Specifically, level 2 may indicate that thewireless communication terminal is capable of receiving an A-MPDU thatincludes one or fewer fragments per MSDU. Level 3 may indicate that thewireless communication terminal is capable of receiving an A-MPDUincluding a plurality of fragments per MSDU. Specifically, level 3 mayindicate that the wireless communication terminal is capable ofreceiving an A-MPDU including four or fewer fragments per MSDU.

In addition, the wireless communication terminal may obtain the right touse the wireless medium through a contention procedure or be granted theright to use the wireless medium. An interval of time during which awireless communication terminal has a right to initiate a frame exchangesequence in a wireless medium is referred to as a transmissionopportunity (TXOP). The TXOP may be defined with a start time and amaximum duration. Also, frames may be exchanged as an immediate responsewithin the TXOP. In this case, the immediate response indicates that theresponse frame is transmitted at predetermined time intervals. Thepredetermined time may be a Short Inter-Frame Space (SIFS). A wirelesscommunication terminal that obtains a TXOP through a contentionprocedure or is granted a TXOP is referred to as a TXOP holder. Also, awireless communication terminal that transmits a frame in response to aframe transmitted from a TXOP holder in a frame exchange sequence isreferred to as a TXOP responder. In this case, the frame may be used asthe MAC frame in the same meaning as the MPDU described above. In orderto prevent any one wireless communication terminal from monopolizing thewireless medium for a long time, the maximum value of the TXOP durationmay be defined. The maximum value of the TXOP duration is referred to asthe TXOP limit. In this case, the TXOP limit may be defined for eachEnhanced Distributed Channel Access Function (EDCAF).

In relation to the fragmentation operation of the wireless communicationterminal, the TXOP limit may be a problem. This will be described withreference to FIGS. 6 to 13.

FIG. 6 shows an operation in which a wireless communication terminalperforms a frame exchange based on a TXOP limit according to anembodiment of the present invention.

The wireless communication terminal may receive an Enhanced DistributedChannel Access (EDCA) parameter set from the base wireless communicationterminal. In this case, the wireless communication terminal may set amanagement information base (MIB) attribute based on the received EDCAparameter set. The wireless communication terminal may exchange framesof data within a duration less than or equal to the TXOP limit. In thiscase, the TXOP limit may be set for each Enhanced Distributed ChannelAccess Function (EDCAF). When the TXOP limit corresponding to the EDCAFof the traffic to be transmitted by the wireless communication terminalis 0, the wireless communication terminal is allowed to transmit onlyone MPDU regardless of the duration of the MPDU. In this case, one MPDUmay represent one A-MPDU. When the TXOP limit corresponding to the EDCAFof the traffic to be transmitted by the wireless communication terminalis not 0, the wireless communication terminal is allowed to transmit thedata or management frame within the TXOP limit. Specifically, when it isdetermined that the wireless communication terminal will exceed the TXOPlimit due to the duration of the data exchange sequence, the wirelesscommunication terminal may transmit the fragment by fragmenting thedata. In this case, the data may indicate an MSDU which is a payload ofa MAC frame. In certain cases, the wireless communication terminal maynot be able to fragment the data. In specific situations, the wirelesscommunication terminal may exceed the TXOP limit. The specific situationmay be a case where the wireless communication terminal transmits onedata (MSDU) or MMPDU. In addition, a specific situation may not includea case where a wireless communication terminal aggregates and transmitstwo or more MPDUs. FIG. 6(a) shows that the wireless communicationterminal fragments the MSDU and transmits fragments within the TXOPlimit. In addition, if the wireless communication terminal attempts totransmit an Aggregate (A)-MSDU and determines that the TXOP limit willbe exceeded due to the transmission of the A-MSDU, the wirelesscommunication terminal may cancel the aggregation of the A-MSDU.Therefore, when the wireless communication terminal attempts to transmitthe A-MSDU, the wireless communication terminal is not allowed to exceedthe TXOP limit.

The wireless communication terminal may exceed the TXOP limit in atleast one of the following situations.

1) When a wireless communication terminal transmits an MSDUcorresponding to a TID with a BlockACK agreement, the wirelesscommunication terminal may transmit an MSDU using a TXOP exceeding aTXOP limit. In this case, the BlockACK agreement may represent anagreement on the BlockACK frame transmission method. In thisspecification, a frame is used to refer to a MAC frame. FIG. 6(b) showsan operation of transmitting an MSDU using a TXOP exceeding a TXOP limitwhen a wireless communication terminal transmits an MSDU correspondingto a TID for which a BlockACK agreement exists.

2) When the wireless communication terminal transmits the previouslytransmitted MPDU again, the wireless communication terminal may transmitthe MPDU using the TXOP exceeding the TXOP limit. In this case, thewireless communication terminal may transmit the same MPDU as thepreviously transmitted MPDU. When the recipient receives an MPDU withthe same sequence number and fragment number as the previously receivedMPDU, the recipient may discard the previously received MPDU. In theembodiment of FIG. 6(c), the wireless communication terminal attempts totransmit the MPDU using Modulation and Coding Scheme 3 (MCS3). Thewireless communication terminal fails to transmit the MPDU andretransmits the same MPDU using the MCS2. In this case, the wirelesscommunication terminal exceeds the TXOP limit to retransmit the sameMPDU.

3) The wireless communication terminal may fragment MSDU, MMPDU, orA-MSDU so that the size of all fragments except for the last fragment isthe same and the size of the last fragment is smaller than that of otherfragments. When the wireless communication terminal generates fragmentsby the maximum number of fragments according to this rule, the wirelesscommunication terminal may transmit the fragments using the TXOPexceeding the TXOP limit. In this case, the maximum number of fragmentsmay be 16. Specifically, when the wireless communication terminalgenerates fragments by the maximum number of fragments at the time pointof attempting to transmit the first fragments, the wirelesscommunication terminal may transmit a fragment using a TXOP exceedingthe TXOP limit regardless of the fragment number of the transmittedfragment. This is because even though the wireless communicationterminal generates the maximum number of fragments allowed for thefragment, the transmission of the fragment exceeds the TXOP limit. Inthe embodiment of FIG. 6(d), the wireless communication terminalgenerates 16 fragments by fragmenting the MSDU or MMPDU. In this case,16 are the maximum number of fragments allowed. Therefore, the wirelesscommunication terminal exceeds the TXOP limit to transmit the fragments.

4) When the wireless communication terminal first transmits a fragmentcorresponding to the MSDU of the previously retransmitted fragment orthe MMPDU of the fragment, the wireless communication terminal maytransmit the fragment using a TXOP exceeding the TXOP limit. In theembodiment of FIG. 6(e), the wireless communication terminal attempts totransmit the first fragment (FN: 0) using MCS3. The wirelesscommunication terminal fails to transmit the fragment, and retransmitsthe first fragment (FN: 0) using MCS2. In this case, the wirelesscommunication terminal retransmits the first fragment (FN: 0) using theTXOP exceeding the TXOP limit. Further, after the wireless communicationterminal retransmits the first fragment (FN: 0), the wirelesscommunication terminal transmits a first fragment (FN: 0) and a secondfragment (FN: 1), which is a fragment of the corresponding MSDU or thecorresponding MMPDU, using a TXOP exceeding the TXOP limit. In thiscase, the second fragment (FN: 1) is a fragment that is initiallytransmitted among the fragments of the corresponding MSDU or thecorresponding MMPDU after transmitting the first fragment (FN: 0).

5) When the wireless communication terminal is not capable offragmenting the MSDU or MMPDU, the wireless communication terminal maytransmit the MSDU or MMPDU using the TXOP exceeding the TXOP limit.Specifically, the wireless communication terminal is not capable offragmenting the group addressed MMPDU. Further, the wirelesscommunication terminal is not capable of fragmenting the control frame.In the embodiment of FIG. 6(f), the wireless communication terminal isnot capable of fragmenting the MSDU or MMPDU. Therefore, the wirelesscommunication terminal transmits the MSDU or MMPDU using the TXOPexceeding the TXOP limit.

In the above description, the wireless communication terminal may be aTXOP holder. In addition, the wireless communication terminal exceedingthe TXOP limit may represent that the wireless communication terminalperforms the transmission using the TXOP exceeding the TXOP limit.

FIG. 7 shows that a wireless communication terminal according to anembodiment of the present invention dynamically performs fragmentation.

The wireless communication terminal may perform dynamic fragmentation aswell as static fragmentation. The static fragmentation indicates thatthe wireless communication terminal generates fragments such that thesize of all the fragments except for the last fragment is the same andthe size of the last fragment is smaller than the size of the otherfragments. Static fragments refer to fragments generated by staticfragmentation. Dynamic fragmentation represents a fragmentation in whichwireless communication terminals are not required to have the same sizeof each fragment. Specifically, in the dynamic fragmentation, thewireless communication terminal is not required to equally fragment thesize of all the fragments except the last fragment. Dynamic fragmentsrefer to fragments generated by dynamic fragmentation.

In dynamic fragmentation, a wireless communication terminal may operateaccording to at least one of the following principles. 1) The wirelesscommunication terminal signals whether the wireless communicationterminal supports dynamic fragmentation. 2) The wireless communicationterminal should transmit the first fragment equal to or greater than theminimum size signaled by the recipient. 3) The wireless communicationterminal may set the fragment level for each TID through the ADDBAextension element in the BlockACK agreement process. 4) The wirelesscommunication terminal may fragment the A-MSDU. 5) When thefragmentation level is Level 2 or Level 3, the wireless communicationterminal may transmit one fragment of the MMPDU per A-MPDU. When thefragmentation level is level 1, the wireless communication terminal maytransmit the fragment of the MMPDU using a single MPDU (S-MPDU).

The wireless communication terminal may determine the fragmentationlevel on the traffic to be transmitted through the BLOCKACK agreementwith the recipient, and may fragment the traffic to be transmittedaccording to the determined fragmentation level. When there is noBLOCKACK agreement for the recipient for the traffic to be transmittedby the wireless communication terminal, the wireless communicationterminal may perform dynamic fragmentation according to the determinedfragmentation level based on the capability of the recipient. In thiscase, the wireless communication terminal may determine the capabilityof the recipient based on the Capabilities Information field transmittedby the recipient. In a specific embodiment, when the value of theCapabilities Information field of the recipient is a predetermined valueeven though there is no BLOCKACK agreement, the wireless communicationterminal may transmit the fragmented MMPDU or MSDU to the recipientaccording to the fragmentation level 1. In this case, the predeterminedvalue may be 1. In addition, when the value of the CapabilitiesInformation field of the recipient is a predetermined value even thoughthere is no BLOCKACK agreement, the wireless communication terminal maytransmit the fragmented MMPDU or MSDU to the recipient according to thefragmentation level 1 or level 2. In this case, the predetermined valuemay be 2. In a specific embodiment, when the value of the CapabilitiesInformation field of the recipient is a predetermined value even thoughthere is no BLOCKACK agreement, the wireless communication terminal maytransmit the fragmented MMPDU or MSDU to the recipient according to thefragmentation level 1 or level 3. In this case, the predetermined valuemay be 3. In the embodiment of FIG. 7, there is no BLOCKACK agreementbetween an originator and a recipient. In this case, the originatordetermines the fragmentation level as level 1 based on the value of theCapabilities Information field transmitted by the recipient. Theoriginator generates three dynamic fragments according to fragmentlevel 1. In these embodiments, the wireless communication terminal maytransmit the sequence and the fragment according to the sequence numberand the fragment number order. In this case, when the wirelesscommunication terminal receives the fragment of a specific sequencebefore a fragment that is included in the same sequence and has afragment number that is smaller than the fragment number of thecorresponding fragment, the wireless communication terminal may deleteall the MPDUs including the fragments of the corresponding sequence fromthe cache. In addition, when the wireless communication terminalreceives a specific sequence before a sequence having a sequence numbersmaller than the sequence number of the corresponding sequence, thewireless communication terminal may delete all MPDUs including thecorresponding sequence from the cache.

In addition, a case where there is no BLOCKACK agreement with therecipient for the traffic to be transmitted by the wirelesscommunication terminal may include a case where the wirelesscommunication terminal transmits the MMPDU. In addition, a case wherethere is no BLOCKACK agreement with the recipient for the traffic to betransmitted by the wireless communication terminal may include a case oftransmitting the MPDU corresponding to the TID designated by QoS No Ack.Since the retransmission is not required for the MPDU corresponding tothe QoS No Ack, the wireless communication terminal may not apply theTXOP limit exception operation to the MPDU corresponding to the QoS NoAck.

When the originator and recipient negotiate dynamic fragmentation forone or more TIDs, the originator can fragment the traffic to betransmitted to the recipient according to the fragmentation level of theTID signaled in the highest fragmentation level among one or more TIDs.In this case, originator and recipient may negotiate dynamicfragmentation using ADDBA extension. In addition, the recipient maysignal the fragmentation level per TID using the ADDBA response.

As described above, when the wireless communication terminal usesdynamic fragmentation, the wireless communication terminal may generatethe fragment more flexibly than when using the static fragmentation.Even in situations where the wireless terminal does not comply with theTXOP limit when using static fragmentation, the wireless terminal mayuse the dynamic fragmentation to comply with the TXOP limit. Inaddition, when the wireless communication terminal uses the dynamicfragmentation, there is a possibility that the wireless communicationterminal can perform transmission while corrupting the fairness with theother wireless communication terminals in an exception condition to theTXOP limit. Therefore, it is necessary to newly define the TXOP limitrelated operation of the wireless communication terminal.

In relation to the retransmission of the wireless communication terminalthrough FIGS. 8 to 11, a case where the wireless communication terminalperforms retransmission using the TXOP exceeding the TXOP limit will bedescribed. In this specification, the fact that the wirelesscommunication terminal exceeds the TXOP limit may refer to performing adata exchange sequence from the start time point of the TXOP to themaximum duration indicated by the TXOP limit.

FIG. 8 shows an operation of a wireless communication terminal accordingto an embodiment of the present invention to determine a recipientreception failure and a retransmission operation.

When a wireless communication terminal according to an embodiment of thepresent invention transmits a frame indicating whether data is received,such as an ACK frame, a Compressed (C)-BA, and a Multi-Station (M)-BAframe, using an A-MPDU, the wireless communication terminal may insert aframe indicating whether it is received into the first MPDU of theA-MPDU. In this case, whether it is received may indicate that thewireless communication terminal successfully receives the traffic.Successful reception of the traffic may indicate that the trafficreceived by the wireless communication terminal is verified by theverification using the Frame Check Sequence (FCS) field. Also,successful transmission in this specification may indicate that thetraffic transmitted by the wireless communication terminal is verifiedby the verification of the recipient using the FCS field. Therefore, thewireless communication terminal according to an embodiment of thepresent invention may determine whether the reception of the recipientis successful based on whether the A-MPDU received by the wirelesscommunication terminal includes a frame indicating whether it isreceived or not at a predetermined position. Specifically, when theA-MPDU received by the wireless communication terminal does not includea frame indicating whether it is received, the wireless communicationterminal may determine that the recipient fails to receive the trafficpreviously transmitted by the wireless communication terminal. Inaddition, the wireless communication terminal according to an embodimentof the present invention may determine whether the recipient fails toreceive the traffic previously transmitted by the wireless communicationterminal based on the BA bitmap field included in the frame indicatingwhether it is received. Specifically, when each bit of the BA bitmapfield of the BA frame received by the wireless communication terminalindicates 0, the wireless communication terminal may determine that thetransmission of the traffic corresponding to the bit fails. In thiscase, the BA frame may be any one of an M-BA frame, a C-BA frame, and ageneral BA frame.

In the embodiment of FIG. 8, the access point transmits a trigger framethat triggers the uplink transmission of the first station. The firststation receives the trigger frame and transmits a trigger-based PPDU(HE TB PPDU) based on the trigger frame. In this case, the access pointfails to receive one MPDU (SN: 2) included in the trigger-based PPDU.The access point transmits a multi-user PPDU (HE MU PPDU) including a BAframe indicating whether the MPDU received from the first station isreceived.

The wireless communication terminal according to an embodiment of thepresent invention can distinguish an ACK frame transmission failure of arecipient from a transmission failure of a wireless communicationterminal through such embodiments. When the wireless communicationterminal retransmits the traffic with an MCS lower than the MCS usedpreviously, the wireless communication terminal may fragment the trafficthat failed to be transmitted and transmit the fragment having thechanged size. Thus, the wireless communication terminal may retransmitthe traffic without exceeding the TXOP limit. This will be describedwith reference to FIG. 9.

FIGS. 9 to 10 illustrate operations in which a wireless communicationterminal according to an embodiment of the present invention performsretransmission within a TXOP limit.

When the wireless communication terminal retransmits the fragment, thewireless communication terminal may perform different retransmissionoperations based on whether the recipient successfully receives afragment having a fragment number that is larger than the fragmentnumber of the fragment that the recipient fails to receive in thesequence including the fragment that the recipient fails to receive. Forconvenience of explanation, the fragment that the recipient fails toreceive are referred to as the failed fragment. In addition, a fragmenthaving a fragment number larger than the fragment number of the failedfragment is referred to as a fragment following the failed fragment.When it is not known that whether the wireless communication terminalreceives an ACK for a fragment following the failed fragment or therecipient receives a fragment following the failed fragment, thewireless communication terminal is not allowed to generate a fragmenthaving sizes different from the size of the failed fragment forretransmission. In this case, the wireless communication terminal mayretransmit the fragment having a size equal to the size of the failedfragment. In addition, the wireless communication terminal may transmitthe fragment having a size equal to the size of the failed fragmentwithin the TXOP limit.

Based on at least one of whether the wireless communication terminaldoes not transmit a fragment following the failed fragment and whetherthe recipient explicitly fails to receive a fragment following thefailed fragment, the wireless communication terminal may generate afragment having a size different from the size of the failed fragmentfor retransmission. In this case, instead of retransmitting the failedfragment, the wireless communication terminal may retransmit thefragment having a size different from the size of the failed fragment.Specifically, when the wireless communication terminal fails to transmita fragment following the failed fragment, or when the recipientexplicitly fails to receive a fragment following the failed fragment,the wireless communication terminal may generate a fragment having asize different from the size of the failed fragment for retransmission.In a specific embodiment, the wireless communication terminal may againfragment the failed fragment. Also, the wireless communication terminalmay allocate the same fragment number as the fragment number of thefailed fragment and the same sequence number as the sequence number ofthe failed fragment to a fragment having a size different from the sizeof the failed fragment. Also, instead of retransmitting the failedfragment, the wireless communication terminal may transmit a fragmenthaving a size different from the size of the failed fragment using aTXOP exceeding the TXOP limit.

In the embodiment of FIG. 9, the wireless communication terminaltransmits a fragment having a fragment number of 0 using the MCS3. Thewireless communication terminal determines that the recipient explicitlyfails to receive the reception of the fragment having the fragmentnumber of 0. Therefore, a fragment having a fragment number of 0 is afailed fragment. A fragment having a larger fragment number than thefailed fragment in the same sequence is not transmitted. Therefore, thewireless communication terminal generates a fragment having a smallersize than the failed fragment for retransmission, and allocates afragment number 0 to the generated fragment. Instead of transmitting thesame fragment as the previously transmitted fragment, the wirelesscommunication terminal transmits the generated fragment with the MCS2.In this case, the wireless communication terminal transmits thegenerated fragment within the TXOP limit.

In addition, the recipients may fail to receive a plurality of fragmentsincluded in the same sequence and having successive fragmentationnumbers. In this case, the wireless communication terminal may generatea fragment having a different size from at least one of the plurality offailed fragments for retransmission regardless of whether the recipientsuccessfully receives fragments following the plurality of failedfragments. Specifically, the wireless communication terminal may changethe size of a failed fragment regardless of whether the recipientsuccessfully receives a fragment following the plurality of failedfragments.

In the embodiment of FIG. 10, the access point transmits a trigger framethat triggers the uplink transmission of the first wirelesscommunication terminal. The first station receives the trigger frame andtransmits a trigger-based PPDU (HE TB PPDU) based on the trigger frame.In this case, the trigger-based PPDU includes an A-MPDU including threefragments having the fragment numbers 1, 2, and 3 included in the samesequence. The access point receives the trigger-based PPDU (HE TB PPDU)from the first station. In this case, the access point fails to receivea fragment having a fragment number of 0 and a fragment having afragment number of 1. The access point transmits a multi-user PPDUincluding an M-BA frame that explicitly indicates the reception failureof the fragment having the fragment number of 0 and the fragment havingthe fragment number of 1. Since the transmission of two fragments withsuccessive fragment numbers fails, the first station generates afragment having a size different from the size of the failed fragmentfor retransmission and allocates a fragment number 0 to the generatedfragment. The wireless communication terminal transmits the generatedfragment within the TXOP limit.

FIG. 11 shows an operation in which a wireless communication terminalaccording to another embodiment of the present invention retransmitsfragments included in the same sequence as a retransmitted fragmentafter retransmission within a TXOP limit.

As described above, when the wireless communication terminal firsttransmits a fragment corresponding to the MSDU of the retransmittedfragment or the MMPDU of the fragment after retransmission, the wirelesscommunication terminal may transmit the fragment using a TXOP exceedingthe TXOP limit. When the wireless communication terminal lowers the MCSto retransmit due to a failure in the previous transmission, this isbecause there is a high possibility of maintaining the lowered MCS evenafter the retransmission. When the wireless communication terminal usesdynamic fragmentation, the wireless communication terminal may adjustthe size of the fragment to be transmitted after retransmission.Therefore, when the wireless communication terminal uses dynamicfragmentation, even if the wireless communication terminal firsttransmits the fragment corresponding to the MSDU of the previouslyretransmitted fragment or the MMPDU of the fragment afterretransmission, it may not be allowed for the wireless communicationterminal to transmit the corresponding fragment using a TXOP exceedingthe TXOP limit. Specifically, when the wireless communication terminaluses dynamic fragmentation, even if the wireless communication terminalfirst transmits the fragment corresponding to the MSDU of the previouslyretransmitted fragment or the MMPDU of the fragment afterretransmission, the wireless communication terminal may transmit thecorresponding fragment only within a TXOP limit.

In the embodiment of FIG. 11, the wireless communication terminaltransmits a fragment having a fragment number of 0 with the MCS3. Therecipient fails to receive a fragment having a fragment number of 0. Afragment having a fragment number greater than 0 is not generated in thesame sequence. Therefore, the wireless communication terminalregenerates the fragment having a smaller size than the size of thetransmission failed fragment, and allocates the fragment number 0 to thegenerated fragment. The wireless communication terminal transmits thecorresponding fragment with the MCS2 within the TXOP limit. Also, thewireless communication terminal generates a fragment of the samesequence as the transmission failed fragment, and allocates the fragmentnumber 1 to the generated fragment. Since the wireless communicationterminal first performs transmission after retransmission but usesdynamic fragmentation, the wireless communication terminal transmits afragment having a fragment number of 1 within the TXOP limit.

FIGS. 12 to 13 show a transmission operation exceeding a TXOP limit whena wireless communication terminal according to an embodiment of thepresent invention uses dynamic fragmentation.

When the wireless communication terminal generates fragments by themaximum number that may be generated by the dynamic fragmentation, thewireless communication terminal may transmit the last generated fragmentamong the generated fragments using the TXOP exceeding the TXOP limit.In addition, the maximum number of fragments that the wirelesscommunication terminal is capable of generating in dynamic fragmentationmay be 16. Therefore, the wireless communication terminal may transmitthe 16th frame of traffic using the TXOP exceeding the TXOP limit. Also,the traffic may be an MSDU, an MMPDU, or an A-MSDU as described above.In a specific embodiment, the wireless communication terminal maydetermine the level of fragmentation as level 1 or level 2 and fragmentthe MSDU, MMPDU or A-MSDU according to the determined fragmentationlevel. In addition, the wireless communication terminal may be a TXOPholder. In addition, when the wireless communication terminal transmitsthe trigger-based PPDU based on the trigger frame, the wirelesscommunication terminal may fragment the A-MSDU to transmit. In thiscase, the wireless communication terminal is not a TXOP holder.Therefore, even in this case, the wireless communication terminal maytransmit the last generated fragment among the fragments generated usingthe TXOP exceeding the TXOP limit.

In the embodiment of FIG. 12, the wireless communication terminalgenerates fragments by dynamically fragmenting the traffic, andtransmits the generated fragments. In this case, the wirelesscommunication terminal generates 16 fragments that are the maximumnumber of fragments that can be generated by the wireless communicationterminal. The wireless communication terminal transmits the 16thtransmission frame using the TXOP exceeding the TXOP limit.

As described above, when the wireless communication terminal generatesthe first dynamic fragment in the dynamic fragmentation, the wirelesscommunication terminal may be required to generate a dynamic fragmenthaving a size greater than or equal to the minimum size specified by therecipient. In this case, the first dynamic fragment represents the firstgenerated dynamic fragment. Therefore, when the wireless communicationterminal generates the first dynamic fragment based on the value thatthe recipient specifies as the minimum size of the fragment, thewireless communication terminal may transmit the first dynamic fragmentusing a TXOP exceeding the TXOP limit. Specifically, when the wirelesscommunication terminal generates the first dynamic fragment based on thevalue specified by the recipient as the minimum size of the fragment,and transmits the first dynamic fragment without using the A-MPDUincluding a plurality of MPDUs, the wireless communication terminal maytransmit the first dynamic fragment using a TXOP exceeding the TXOPlimit. The case where a wireless communication terminal transmits afirst dynamic fragment without using an A-MPDU including a plurality ofMPDUs may represent a case where a fragment is transmitted by using asingle MPDU. In addition, the wireless communication terminal may belimited to generating the first dynamic fragment having a size equal tothe value that the recipient specifies as the minimum size of thefragment. This is because, if the wireless communication terminalgenerates a dynamic fragment having an excessively large size, thefairness with other wireless communication terminals may be a problem.

In the embodiment of FIG. 13, the wireless communication terminalgenerates a plurality of fragments by dynamically fragmenting thetraffic. In this case, the wireless communication terminal generates thefirst generated fragment (FN: 0) with the minimum fragment sizedesignated by the recipient. The wireless communication terminaltransmits the corresponding fragment to the recipient using the TXOPexceeding the TXOP limit. Then, the wireless communication terminaltransmits the second and third transmitted fragments FN: 1 and FN: 2within the TXOP limit.

Further, in the specific embodiment, when the wireless communicationterminal transmits the first fragment of the A-MSDU, the embodiment ofthe TXOP limit compliance exception described with reference to FIG. 13may not apply. This is because there is a high possibility that thewireless communication terminal can disassemble the A-MSDU.

The embodiments described with reference to FIGS. 5 to 13 may be appliedto the transmission operation of the TXOP holder. There is a case wherea wireless communication terminal that is not a TXOP holder can transmitdata. Specifically, when a wireless communication terminal participatesin an uplink (UL) multi-user (MU) transmission, a wireless communicationterminal that is not a TXOP holder may also transmit data. In such away, if the originator that is not the TXOP holder transmits data, theoriginator's TXOP limit related operation is problematic. This will bedescribed with reference to FIGS. 14 to 16.

FIG. 14 shows a retransmitting operation of a wireless communicationterminal, not a TXOP holder, according to an embodiment of the presentinvention.

When the wireless communication terminal participates in UL MUtransmission, the wireless communication terminal may transmit data evenif the wireless communication terminal is not a TXOP holder. In thiscase, the wireless communication terminal can set the TXOP limitdifferently from TXOP limit of the base wireless communication terminalwhich is the TXOP holder. Therefore, there is a possibility that thewireless communication terminal increases the efficiency of UL MUtransmission by using a TXOP which is much larger than the TXOP limitused in single user (SU) transmission. The wireless communicationterminal may perform the uplink transmission using the TXOP which ismuch larger than the TXOP limit used in the SU transmission and the basewireless communication terminal may not successfully receive the datatransmitted through the uplink transmission. In this case, the wirelesscommunication terminal can attempt retransmission using a very largeTXOP once again. Therefore, when the wireless communication terminal isallowed to perform retransmission using the TXOP exceeding the TXOPlimit when performing retransmission, this can damage the fairness withother wireless communication terminals. In order to prevent this, whenthe wireless communication terminal attempts retransmission due to UL MUtransmission failure, the wireless communication terminal may performretransmission only using UL MU transmission.

In the embodiment of FIG. 14, a wireless communication terminal that isnot a TXOP holder transmits one fragment (FN: 0) to a base wirelesscommunication terminal through UL MU transmission. The base wirelesscommunication terminal transmits an M-BA frame M-BA indicating that thewireless communication terminal does not successfully receive onefragment (FN: 0). The wireless communication terminal receives the M-BAframe from the base wireless communication terminal. The wirelesscommunication terminal fails to transmit the MU. Therefore, the wirelesscommunication terminal transmits a fragment (FN: 1) other than thefragment (FN: 0) that fails to be transmitted through the SUtransmission.

The embodiment described with reference to FIG. 14 may be applied totransmission in addition to UL MU transmission. This is because inaddition to the UL MU transmission, a wireless communication terminalthat is not the TXOP holder can transmit data. Specifically, when thebase wireless communication terminal and the wireless communicationterminal use the reverse direction method during one-to-onetransmission, the wireless communication terminal that is not the TXOPholders can also transmit data. This will be described with reference toFIGS. 15 to 16.

FIGS. 15 to 16 show a retransmitting operation of a wirelesscommunication terminal, not a TXOP holder, according to anotherembodiment of the present invention.

The effect of retransmission of MPDUs transmitted in UL MU transmissionand retransmission of MPDUs transmitted in reverse directiontransmission on TXOP management may be very small. Therefore, when theretransmission is retransmission for transmission failure using thetrigger-based PPDU, the wireless communication terminal may perform theretransmission only using the trigger-based PPDU.

In the embodiment of FIG. 15, a wireless communication terminal that isnot a TXOP holder transmits one fragment (FN: 0) to a base wirelesscommunication terminal through UL MU transmission. The base wirelesscommunication terminal transmits an M-BA frame M-BA indicating that thewireless communication terminal does not successfully receive onefragment (FN: 0). The wireless communication terminal receives the M-BAframe from the base wireless communication terminal. The wirelesscommunication terminal fails in transmission using the trigger-basedPPDU. Therefore, the wireless communication terminal transmits afragment (FN: 1) other than the fragment (FN: 0) that failed to betransmitted through the SU transmission.

When following the embodiments described with reference to FIGS. 14 to15, the wireless communication terminal can not retransmit all the MPDUstransmitted in the UL MU using the SU transmission. If the wirelesscommunication terminal attempts retransmission due to transmissionfailure using the trigger-based PPDU and the duration of thetransmission sequence required for retransmission of the wirelesscommunication terminal does not exceed the TXOP limit, the wirelesscommunication terminal can perform the corresponding retransmission byusing the SU transmission. In this case, the transmission sequencerequired for retransmission may include a predetermined time intervalbetween retransmission and response transmission for retransmission, anda time required to receive a response to retransmission. Specifically,the response to the retransmission may be an immediate response that istransmitted within a predetermined time from the reception of the framethat is the response target. Also, the predetermined time intervalbetween retransmission and response transmission for retransmission maybe Short Inter-Frame Space (SIFS). The response to retransmission may bean ACK frame. In this case, the time required for the retransmissionsequence may be calculated based on the MCS used in the UL MUtransmission. Further, the time required for the retransmission sequencemay be calculated based on the specific frequency bandwidth. In thiscase, the specific frequency bandwidth may be the maximum frequencybandwidth allowed in the SU transmission in the BSS including thewireless communication terminal. In addition, the specific frequencybandwidth may be 20 MHz. In addition, the specific frequency bandwidthmay be a frequency bandwidth in which the size of an Resource Unit (RU)used in UL MU transmission is rounded up to a multiple of 20 MHz.

In the embodiment of FIG. 16, a wireless communication terminal that isnot a TXOP holder transmits one fragment (FN: 0) to a base wirelesscommunication terminal through UL MU transmission. The base wirelesscommunication terminal transmits an M-BA frame M-BA indicating that thewireless communication terminal does not successfully receive onefragment (FN: 0). The wireless communication terminal receives the M-BAframe from the base wireless communication terminal. The wirelesscommunication terminal fails to transmit the MU. The wirelesscommunication terminal calculates the time required for the transmissionsequence required for retransmission of one fragment (FN: 0). The timerequired for the transmission sequence calculated by the wirelesscommunication terminal exceeds the TXOP limit. Therefore, the wirelesscommunication terminal transmits a fragment (FN: 1) other than thefragment (FN: 0) that fails to be transmitted through the SUtransmission.

In order for a wireless communication terminal to perform Multi InputMulti Output (MIMO) or beamforming, it is required to receive a channelstate from a recipient. A wireless communication terminal that is toperform MIMO or beamforming receives a channel state through a soundingprotocol sequence as follows. For convenience of explanation, a wirelesscommunication terminal that is to perform MIMO or beamformingtransmission is referred to as a beamformer, and a wirelesscommunication terminal that is to perform MIMO or beamforming receptionis referred to as a beamformee. The beamformer transmits a Null DataPacket Announcement (NDPA) frame to indicate that the sounding protocolsequence is initiated. In this case, the NDPA frame may includeinformation on a beamformee, which is a wireless communication terminalis to measure a channel state. The beamformer transmits a Null DataPacket (NDP) frame, which is used for measuring the channel state anddoes not include a data field. In this case, the beamformer may transmitthe NDP frame after a predetermined time from the transmission of theNDPA frame. At this point, the predetermined time may be a SIFS. Thebeamformee measures the channel state based on the NDP frame. Thebeamformee transmits a feedback frame indicating the measured channelstate to the wireless communication terminal that transmitted the NDPframe. In this case, the feedback frame may be a compressed feedbackframe including a compressed type field rather than a general feedbackframe. Since the size of the feedback frame can be very large, thebeamformee is required to occupy the wireless medium for a long time.Therefore, if the beamformer sets a very small TXOP limit on the ACattempting to transmit a frame that starts a sounding sequence, soundingprotocol sequence may not be completed within the TXOP limit. Therefore,since the sounding protocol sequence is an operation that is essentialfor MIMO and beamforming transmission, an exception to the TXOP limitmay be allowed. However, if the exception to the TXOP limit is widelyapplied in the sounding protocol sequence, the fairness with otherwireless communication terminals may be a problem. Therefore, there is aproblem in the operation of the wireless communication terminal relatedto the TXOP limit in the sounding protocol sequence.

FIGS. 17 to 18 show that the wireless communication terminal accordingto an embodiment of the present invention performs the sounding protocoloperation in relation to the TXOP limit.

The beamformer may transmit NDPA frame and NDP frame using the TXOPexceeding the TXOP limit. Specifically, when an NDP frame is transmittedwithin a TXOP limit, the beamformer may transmit an NDPA frame and anNDP frame using a TXOP exceeding the TXOP limit. Also, the beamformermay receive the feedback frame in response to the NDP frame from thebeamformee within a TXOP exceeding the TXOP limit. The interval betweentransmission of the NDPA frame and transmission of the NDP frame may bea SIFS. In addition, the time interval between the NDP frame and thefeedback frame may be a SIFS. Specifically, the beamformee may transmitthe feedback frame after a SIFS from when the NDP frame is received.

Further, when the feedback frame exceeds the maximum A-MPDU length, thebeamformee may fragment the feedback frame into a plurality of segmentsand transmit the segments. In this case, in order to request asubsequent segment for a previously transmitted feedback frame, thebeamformer may transmit a Beamforming Report Poll (BRP) frame to thebeamformee. In this case, the beamformer may transmit a BRP frame usinga TXOP exceeding the TXOP limit. Specifically, when the beamformertransmits a BRP frame within the TXOP limit, the beamformer may transmitthe BRP frame using a TXOP exceeding the TXOP limit. Also, thebeamformer may receive the feedback frame from the beamformee within aTXOP exceeding the TXOP limit. The time interval between the BRP frameand the feedback frame may be a SIFS. Specifically, the beamformee maytransmit the feedback frame after a SIFS from when the BRP frame isreceived.

In the embodiment of FIG. 17, the beamformer transmits an NDPA frame HENDPA and an NDP frame HE NDP within the TXOP limit. Since the beamformertransmits the NDPA frame HE NDPA and the NDP frame HE NDP within theTXOP limit, the beamformer may transmit NDPA frame HE NDPA and NDP frameHE NDP using the TXOP exceeding the TXOP limit. Specifically, thebeamformer receives the feedback frame SU Compressed Feedback within aTXOP exceeding the TXOP limit. The beamformee transmits the feedbackframe after a SIFS from when the NDP frame HE NDP is received.

In addition, the beamformer may transmit a BRP trigger frame to solicitfeedback frames from a plurality of beamformers. Specifically, thebeamformer may transmit an NDPA frame indicating a plurality ofbeamformees. In this case, the NDPA frame may include a plurality ofuser info fields each indicating the plurality of beamformees. Also, theReceiver Address (RA) of the NDPA frame may be a broadcast address.After a predetermined time from when the beamformer transmits the NDPAframe, the beamformer transmits the NDP frame. After transmitting theNDP frame, the BRP trigger frame may be transmitted. In this case, thepredetermined time may be a SIFS. The beamformer may receive the BRPtrigger frame after a predetermined time from the transmission of theNDP frame. In this case, the predetermined time may be a SIFS. Theplurality of beamformers may receive the BRP trigger frame and transmitthe feedback frames simultaneously after a predetermined time from whenthe BRP trigger frame is received. In this case, the predetermined timemay be a SIFS. Also, the plurality of beamformees may simultaneouslytransmit feedback frames using orthogonal frequency multiple access(OFDMA). If the beamformer transmits a BRP trigger frame and the TXOPlimit is applied without exception, it may be difficult for thebeamformer to trigger the transmission of the feedback frames of aplurality of beamformers. Therefore, the beamformer may have to performa sounding protocol sequence separately for each beamformee. In relationto these problems, the wireless communication terminal may operateaccording to the following specific embodiments.

The beamformer may transmit a BRP trigger frame using a TXOP exceedingthe TXOP limit. In a specific embodiment, the beamformer may transmit anNDPA frame, an NDP frame, and a BRP trigger frame using a TXOP exceedingthe TXOP limit. In this case, when the beamformer transmits an NDPAframe, an NDP frame, and a BRP trigger frame within the TXOP limit, thebeamformer may transmit NDPA frames, NDP frames, and BRP trigger framesusing a TXOP exceeding the TXOP limit. As described above, thetransmission interval between the NDPA frame, the NDP frame, and the BRPtrigger frame may be a SIFS. In addition, the time interval between theBRP trigger frame and the feedback frame may be a SIFS. Specifically,the beamformee may transmit the feedback frame after a SIFS from whenthe BRP trigger frame is received.

When the beamformer uses the BRP trigger frame to trigger thetransmission of many beamformee feedback frames, the fairness withexisting sounding protocol sequences may be a problem. The wirelesscommunication terminal may operate according to the following specificembodiments considering the fairness with the existing sounding protocolsequence.

In another specific embodiment, although the beamformer uses NDPA framesto indicate a plurality of beamformees, the beamformer may trigger thetransmission of feedback frames from a specific number of beamformee inthe BRP trigger frame. In this case, the specific number may be 1. Also,the specific number may be set based on the TXOP limit. In addition, theBRP trigger frame may include a predetermined number of User Infofields. Thus, the beamformer receives feedback frames from thepredetermined number of beamformees. In the next TXOP of the TXOP thattransmitted the first BRP trigger frame, the beamformer may transmit theBRP trigger frame again to trigger transmission of the feedback framesfrom a specific number of beamformees among the remaining beamformeesother than the beamformees previously indicated by the BRP trigger frameamong the plurality of beamformees indicated by the NDPA frame. In thiscase, the BRP trigger frame may include a User Info field indicatingeach of a specific number of beamformees among the remaining beamformeesother than the beamformee previously indicated by the BRP trigger frameamong the plurality of beamformees indicated by the NDPA frame. Also, inthe next TXOP of the TXOP in which the first BRP trigger frame istransmitted, the beamformer may not transmit the NDPA frame and the NDPframe again. Also, in the next TXOP of the TXOP in which the beamformertransmitted the first BRP trigger frame, when the beamformer transmitsthe BRP trigger frame within the TXOP limit, the beamformer may transmitthe BRP trigger frame using a TXOP exceeding the TXOP limit.Specifically, the beamformee may transmit the feedback frame after aSIFS from when the BRP trigger frame is received.

Also, in the above embodiments, the beamformee may transmit the feedbackframe in response to the BRP trigger frame using the trigger-based PPDU.

In the embodiment of FIG. 18, the beamformer transmits an NDPA frame HENDPA and an NDP frame HE NDP within the TXOP limit. In this case, theNDPA frame HE NDPA indicates a plurality of beamformers. Also, thebeamformer transmits a first BRP trigger frame (Beamforming Report Polltrigger variant) after a SIFS from when transmitting the NDP frame HENDP. In this case, the BRP trigger frame (Beamforming Report Polltrigger variant) indicates one beamformee. The beamformer receives atrigger-based PPDU (HE TP PPDU compressed feedback) including a feedbackframe from the beamformee. In this case, the trigger-based PPDU (HE TPPPDU compressed feedback) including a feedback frame may be transmittedto the SIFS from when the beamformee receives the first BRP triggerframe (Beamforming Report Poll trigger variant). In the next TXOP, thebeamformer transmits a second BRP trigger frame (Beamforming Report Polltrigger variant). In this case, the second BRP trigger frame(Beamforming Report Poll trigger variant) indicates any of the remainingbeamformees other than the beamformee indicated by the first BRP triggerframe (Beamforming Report Poll trigger variant) among the plurality ofbeamformees indicated by the NDPA frame HE NDPA. Since the beamformertransmits a second BRP trigger frame (Beamforming Report Poll triggervariant) within the TXOP limit, the beamformer transmits the second BRPtrigger frame (Beamforming Report Poll trigger variant) using a TXOPexceeding the TXOP limit. Specifically, the beamformer receives atrigger-based PPDU (HE TP PPDU compressed feedback) including a feedbackframe within the TXOP exceeding the TXOP limit. In this case, thebeamformer receives the trigger-based PPDU (HE TP PPDU compressedfeedback) including the feedback frame from the beamformee indicated bythe second BRP trigger frame (Beamforming Report Poll trigger variant).In this case, the beamformee may transmit a trigger-based PPDU (HE TPPPDU compressed feedback) including a feedback frame after a SIFS fromwhen the beamformee receives the second BRP trigger frame (BeamformingReport Poll trigger variant).

FIG. 19 shows the operation of a wireless communication terminalaccording to an embodiment of the present invention.

The wireless communication terminal performs transmission based on theTXOP limit. Specifically, the wireless communication terminal may obtaininformation on the TXOP limit (S1901), and perform transmission based onthe information on the TXOP limit (S1903). Specifically, the wirelesscommunication terminal may obtain information on the TXOP limit from thebase wireless communication terminal. In this case, the information onthe TXOP limit may be the EDCA parameter set element. The wirelesscommunication terminal may perform transmission according to theprinciple of the TXOP limit described with reference to FIGS. 6 to 7.

The wireless communication terminal may transmit a Beamforming ReportPoll (BRP) trigger frame to another wireless communication terminalusing a TXOP exceeding the TXOP limit. In this case, the wirelesscommunication terminal may receive the feedback frame in response to theBRP trigger frame from another wireless communication terminal withinthe TXOP exceeding the TXOP limit. In this case, the BRP trigger frameis capable of triggering simultaneous transmission of feedback framesfrom one or more wireless communication terminals. The feedback framemay indicate a state of a channel measured by another wirelesscommunication terminal, which is to be used for Multi Input Multi Output(MIMO) transmission of the wireless communication terminal to anotherwireless communication terminal or beamforming transmission of thewireless communication terminal to another wireless communicationterminal. In a specific embodiment, a beamformer preparing for MultiInput Multiple Output (MIMO) transmission or beamforming transmissionmay transmit an NDPA frame, an NDP frame and a BRP trigger frame using aTXOP exceeding the TXOP limit. For example, after the wirelesscommunication terminal transmits a Null Data Packet Announcement (NDPA)frame informing another wireless communication terminal that thesounding protocol sequence is initiated, the wireless communicationterminal may transmit a Null Data Packet (NDP) frame to be used forchannel state measurement to another wireless communication terminal. Inthis case, when the wireless communication terminal transmits the NDPAframe, the NDP frame, and the BRP trigger frame within the TXOP limit,it is possible to transmit the BRP trigger frame to another wirelesscommunication terminal using a TXOP exceeding the TXOP limit after apredetermined time from when the NDP frame is transmitted to anotherwireless communication terminal.

Also, the BRP trigger frame may be for soliciting a subsequent segmentfor a feedback frame previously transmitted by another wirelesscommunication terminal. In this case, when the beamformer transmits aBRP trigger frame within the TXOP limit, the beamformer may transmit theBRP trigger frame using the TXOP exceeding the TXOP limit.

The feedback frame may be transmitted from the another wirelesscommunication terminal after a predetermined time elapses from when theanother wireless communication terminal receives the BRP trigger frame.The predetermined time described above may all be a SIFS. Specifically,the beamformee and the beamformer may operate according to theembodiments described with reference to FIGS. 17 to 18.

The wireless communication terminal may generate at least one fragmentusing dynamic fragmentation and transmit at least one fragment toanother wireless communication terminal. As described above, dynamicfragmentation may indicate fragments that are not required to equallyfragment the size of all fragments except the last fragment.

The wireless communication terminal may determine a fragmentation levelto be applied to a fragment to be transmitted to another wirelesscommunication terminal on the basis of a BlockACK agreement with anotherwireless communication terminal. When there is no BlockACK agreementbetween the wireless communication terminal and another wirelesscommunication terminal, the wireless communication terminal may performdynamic fragmentation according to the fragmentation level determinedaccording to the capabilities of the other wireless communicationterminals. In this case, the fragmentation level may represent thetransmission method of the fragment as described above.

In a specific embodiment, another wireless communication terminal maygenerate a first fragment that is generated first among the at least onefragment based on a value designated by a minimum size of the fragment.In this case, the wireless communication terminal may transmit the firstfragment to another wireless communication terminal using the TXOPexceeding the TXOP limit. When the wireless communication terminaltransmits at least one fragment to another wireless communicationterminal without using an Aggregate (A)-MPDU including a plurality ofMAC Protocol Data Units (MPDUs), it is possible to transmit the firstfragment to another wireless communication terminal using the TXOPexceeding the TXOP limit. In this case, the wireless communicationterminal may generate the first fragment with the same size as the valuedesignated by the minimum size of the fragments of the another wirelesscommunication terminal.

Further, the wireless communication terminal may generate the at leastone fragment by a maximum number that the wireless communicationterminal is capable of generating a fragment, and may transmit a secondfragment, which is the last generated one among the at least onefragment, to another wireless communication terminal using a TXOPexceeding the TXOP limit. In the specific embodiment, the maximum numberthat the wireless communication terminal is capable of generating thefragments may be 16.

When another wireless communication terminal explicitly fails to receivea third fragment, which is one of the at least one fragment, thewireless communication terminal may generate a fourth fragment having adifferent size from the third fragment based on at least one of whetherthe wireless communication dose not transmit a fragment following thethird fragment and whether another wireless communication terminalexplicitly fail to receive a fragment following the third fragment. Thewireless communication terminal may allocate the sequence number and thefragment number of the third fragment to the fourth fragment. In thiscase, the wireless communication terminal may transmit the fourthfragment to another wireless communication terminal instead ofretransmitting the third fragment to another wireless communicationterminal. Specifically, the wireless communication terminal may transmitthe fourth fragment using the TXOP exceeding the TXOP limit. When thewireless communication terminal uses the dynamic fragmentation, thewireless communication terminal may operate as in the embodimentsdescribed with reference to FIGS. 7 to 16.

The wireless communication terminal may be a TXOP holder. In addition,specific operation when the wireless communication terminal is not aTXOP holder may be the same as that shown in FIGS. 14 to 16.

Although the present invention is described by using wireless LANcommunication as an example, it is not limited thereto and may beapplied to other communication systems such as cellular communication.Additionally, while the method, device, and system of the presentinvention are described in relation to specific embodiments thereof,some or all of the components or operations of the present invention maybe implemented using a computer system having a general purpose hardwarearchitecture.

The features, structures, and effects described in the above embodimentsare included in at least one embodiment of the present invention and arenot necessary limited to one embodiment. Furthermore, features,structures, and effects shown in each embodiment may be combined ormodified in other embodiments by those skilled in the art. Therefore, itshould be interpreted that contents relating to such combination andmodification are included in the range of the present invention.

While the present invention is described mainly based on the aboveembodiments but is not limited thereto, it will be understood by thoseskilled in the art that various changes and modifications are madewithout departing from scope of the present invention. For example, eachcomponent specifically shown in the embodiments may be modified andimplemented. It should be interpreted that differences relating to suchmodifications and application are included in the scope of the presentinvention defined in the appended claims.

The invention claimed is:
 1. A wireless communication terminal that wirelessly communicates, the wireless communication terminal comprising: a transceiver for transmitting and receiving a wireless signal; and a processor for processing the wireless signal, wherein the processor is configured to: perform a transmission based on a transmission opportunity (TXOP) limit which is a maximum value of a TXOP, which is a time interval in which a wireless communication terminal has a right to initiate a frame exchange sequence in a wireless medium, use dynamic fragmentation to generate at least one fragment, transmit the at least one fragment to another wireless communication terminal, when the another wireless communication terminal explicitly fails to receive a previously transmitted fragment, which is one of the at least one fragment, based on at least one of whether the wireless communication terminal does not transmit a fragment following the previously transmitted fragment and whether the another wireless communication terminal explicitly fails to receive a fragment following the previously transmitted, generate a retransmission fragment having a size different from the previously transmitted fragment and having a sequence number and a fragment number that are the same as a sequence number and a fragment number of the previously transmitted fragment, and transmit the retransmission fragment to the another wireless communication terminal instead of retransmitting the previously transmitted fragment to the another wireless communication terminal, wherein the dynamic fragmentation represents a fragment that is not a static fragmentation that is required to equally fragment the size of all fragments except the last fragment.
 2. The wireless communication terminal of claim 1, wherein the processor is configured to generate 16 fragments, and transmit a 16th fragment generated last among the 16 fragments to the another wireless communication terminal exceeding the TXOP limit.
 3. The wireless communication terminal of claim 1, wherein when there is no BlockACK agreement between the wireless communication terminal and the another wireless communication terminal, the processor is configured to perform dynamic fragmentation according to a fragmentation level determined according to a capability of the another wireless communication terminal, wherein the fragmentation level indicates a transmission method of a fragment.
 4. The wireless communication terminal of claim 1, wherein the wireless communication terminal is a TXOP holder.
 5. A method of operating a wireless communication terminal that wirelessly communicates, the method comprising: performing a transmission within a transmission opportunity (TXOP) limit which is a maximum value of a TXOP, which is a time interval in which a wireless communication terminal has a right to initiate a frame exchange sequence in a wireless medium, using dynamic fragmentation to generate at least one fragment; when the another wireless communication terminal explicitly fails to receive a previously transmitted fragment, which is one of the at least one fragment, based on at least one of whether the wireless communication terminal does not transmit a fragment following the previously transmitted fragment and whether the another wireless communication terminal explicitly fails to receive a fragment following the previously transmitted, generating a retransmission fragment having a size different from the previously transmitted fragment and having a sequence number and a fragment number that are the same as a sequence number and a fragment number of the previously transmitted fragment, and transmitting the retransmission fragment to the another wireless communication terminal instead of retransmitting the previously transmitted fragment to the another wireless communication terminal, wherein the dynamic fragmentation represents a fragment that is not a static fragmentation that is required to equally fragment the size of all fragments except the last fragment.
 6. The method of claim 5, wherein the method further comprises generating 16 fragments, and transmitting a 16th fragment generated last among the 16 fragments to the another wireless communication terminal exceeding the TXOP limit.
 7. The method of claim 5, the method further comprises when there is no BlockACK agreement between the wireless communication terminal and the another wireless communication terminal, performing dynamic fragmentation according to a fragmentation level determined according to a capability of the another wireless communication terminal, wherein the fragmentation level indicates a transmission method of a fragment.
 8. The method of claim 5, wherein the wireless communication terminal is a TXOP holder. 